In processing color photographic light-sensitive materials for photographing represented by photographic light-sensitive materials containing silver iodobromide as the silver halide, a stabilizer containing formaldehyde is used, in general, in the final processing bath which follows the washing bath.
Formaldehyde used in the stabilizing bath contributes to the improvement in properties of color photographic light-sensitive materials, particularly to the prevention of flaws on the surface of light-sensitive materials and the prevention of gradation changes which are associated with hardening of light-sensitive materials owing to aging. It is also known that formaldehyde has an effect of preventing deterioration in stability of dye images caused by a coupler left unreacted in color light-sensitive materials.
However, formaldehyde added in the stabilizer for the purpose of a stabilized dye image, etc., has a fault of adhering to light-sensitive materials and reacting with sulfite ions brought from the preceding bath to form adducts; this not only impairs the primary object of stabilizing dye images but also accelerates precipitation of sulfur or sulfides.
As a preventive measure against such a problem, U.S. Pat. No. 4,786,583 discloses use of alkanol amines, but alkanol amines are liable to cause yellow stains in unexposed portions and not necessarily satisfactory in preventing sulfur or sulfides from precipitating.
On the other hand, undesirable influences of formaldehyde upon the human body have been disclosed. In the United States, Chemical Industry Institute of Toxicology (CIIT) announced that rats developed naris cancers at a formaldehyde concentration of 15 ppm; National Institute for Occupational Safety and Health (NIOSH) and American Conference of Governmental Industrial Hygientists (ACCIH) also disclosed that formaldehyde might be carcinogenic. Use of formaldehyde is strictly regulated in Europe, too. In Germany, the formaldehyde concentration in residences has been regulated to be not more than 0.1 ppm since 10 years ago.
In Japan, use of formaldehyde is regulated for its toxicity of irritating the mucous membrane by the law for deleterious substances and powerful drugs, regulation to organic solvent toxication, according to the Occupational Safety and Health Law, the regulation on household goods, the regulation on textile goods and plywoods, and the regulation on underwear and baby clothes newly enforced in 1975 by the Ministry of Health and Welfare. Under such circumstances, there has been demanded a technique which enables reduction in amounts of formaldehyde to be used.
As means to make the formaldehyde content in stabilizers substantially zero or to reduce it effectively, there are proposed use of hexahydrotriazine compounds in Japanese Pat. O.P.I. Pub. Nos. 27742/1987 and 151538/1986 and use of N-methylol compounds in U.S. Pat. No. 4,859,574.
Though these hexahydrotriazine compounds can prevent dye images from fading under high temperature and high humidity conditions even when the formaldehyde concentration is substantially zero, these are less effective under low humidity conditions, for example, at a relative humidity not higher than 20%. Moreover, these compounds have a tendency to stain the backside of color light-sensitive materials for photographing due to uneven sagging of a stabilizer used and, further, have a disadvantage of lowering preservability of a stabilizer and are liable to-cause precipitation of sulfur or sulfides, though not so heavy as formaldehyde does; therefore, troubles are apt to arise in the cases of a protracted processing, a small processing amount and a small replenishing amount.
When the above N-methylol compounds are used in place of formaldehyde, these are insufficient not only in preventing fading of dye images and backside stains but also in improving preservability of a stabilizer; moreover, the preservability is noticeably deteriorated if a preventive measure is taken against the fading of dye images.
In a continuous method for processing a large amount of light-sensitive materials in an automatic processor, it is necessary to take a measure for keeping each component of a stabilizer at a constant concentration, in order to avoid deterioration in properties of the stabilizer due to change in concentration of the component. In addition, minimization of the replenishing amount is strongly demanded in recent years from the viewpoints of economy and antipollution.
A stabilizer may be prepared by mixing necessary components when it is used. But in general, to increase efficiency of the preparation, prescribed amounts of processing agents are mixed and dissolved in the form of concentrated solutions beforehand and, at the time of use, these concentrated solutions are mixed with one another and/or diluted with water to a uniform processing solution, which is used as a tank solution or a replenisher.
However, it is found that concentrated compositions containing formaldehyde and N-methylol compounds have a problem in preservability. Further, it is found that, in a high-speed conveyance during the rapid processing with a large-sized automatic processor practiced in recent years, light-sensitive materials become susceptible to flaws because pressure is applied to the lower turn roller in the stabilizing tank of an automatic processor.